Semiconductor technology has allowed for very large, complex computing systems to be integrated onto a very small Integrated Circuit (IC). Power-supply voltages have also been reduced along with power consumption, allowing these IC's to be powered by a battery or even self-powered by harvesting energy from nearby radiation sources such as a Near-Field Communication (NFC) or Radio-Frequency Identification (RFID) transmitter.
Energy can be harvested using inductive coupling of RF signals. The distance between an RFID tag and reader (range) is limited to about 3 meters. Near-Field Communication (NFC) devices purposely limit the range to 20 cm for enhanced security. Users need to almost touch their NFC-enabled device such as a smartphone to a NFC reader to verify a NFC transaction.
More recently, Bluetooth Low-Energy (BLE) tags have been developed, along with the Bluetooth 4.0 protocol. Unlike passive RFID tags, BLE tags are powered by a low-energy source. Apple has further enhanced BLE tags to create iBeacons. iBeacons are powered by a low energy source such as a battery and thus have enough energy to periodically or continuously broadcast a packet to nearby devices. The range is up to 100 meters, but can be reduced by lowering the broadcast power. The broadcast packets are pushed from the iBeacon/BLE tag to nearby devices while data is pulled from passive RFID tags when energized by a RFID reader. RFID, BLE, and NFC co-exist because each has advantages and disadvantages that fit various specialized applications.
Device shrinkage and energy efficiency have enabled wearable computing. IC devices may be worn in clothing or attached to a person's skin with adhesive tape. Some may be disposable to increase hygiene. Various bio-sensors can be attached to the IC, allowing a person's biological signs to be sensed, such as heart rate, temperature, and respiration. Chemical sensors may detect very specific biochemicals, such as DNA markers, blood glucose, or various gases. Some sensors may operate only once when near a RF transmitter, performing a one-shot measurement without battery power. Other sensors may operate continuously on battery power. Some may use NFC, while others use RFID or BLE communication standards.
FIG. 1 shows a nano-wire bio-sensor. Nano-technology has produced specialized biological sensors. Nano-wire 110 is constructed by a semiconductor manufacturing process on silicon substrate 102. Silicon-dioxide (glass) layer 104 and silicon nitride Si3N4 layer 106 grown or deposited on silicon substrate 102.
Nano-wire 110 may be a thin polysilicon layer that terminates in source 114 and drain 112. Walls 116 form an opening to nano-wire 110 to allow chemicals from the environment, such as analytes 120 to reach nano-wire 110. Chemical receptors 118 are bonded onto Nano-wire 110. When analytes 120 bond to receptors 118, electrons are shifted either away from nano-wire 110 or into nano-wire 110, resulting in a reduction or an increase in free carriers within nano-wire 110. The effective resistance of nano-wire 110 thus changes when analytes 120 bond with receptors 118. This bonding may be a weak chemical bond or other kind of physical mechanism, but the change in resistance when analytes 120 are present can be measured when current is drawn between drain 112 and source 114. Silicon substrate 102 may act as a gate to bias nano-wire 110.
Nano-sensor 130 may sense a wide variety of specific chemicals, including large bio-chemicals, by the choice of chemical receptor 118. Four nano-wires 110 may be arranged into a bridge network between power and ground, with two differential sensor outputs from the intermediate nodes. Two of the four nano-wires in the bridge may be exposed to the environment and to any analytes 120, while the other two nano-wires are sealed and prevented from exposure to analytes 120. This bridge nano-wire network is especially sensitive.
A bewildering variety of proprietary IC devices have been developed for the many kinds of bio-sensors. A patient in a hospital may need to be wired up with dozens of sensors, each sensing a different bio-function or bio-chemical, using many different kinds of computing IC devices. These IC devices are often incompatible with each other even when the functions performed are similar. This redundancy of function is not just wasteful but also cumbersome and uncomfortable to the patient whom may have dozens or wires attached to him, making simple movement such as turning in bed difficult.
In the future, as the number of different kinds of bio-sensors expands, hospital patients may feel like a part of a machine as dozens of different kinds of wearable sensors and computing devices are attached. Some sensors may require very accurate multi-bit data conversion and processing, while other sensors may require less intensive data conversion and processing. Some sensors may require continuous monitoring and battery power, while others may sense infrequently and may be able to operate using energy harvesting to avoid using a battery or other power source. Some sensor devices may communicate results wirelessly, with others may require bulky wires.
Multi-sensors that can measures several biological signs at a time are desirable. Sensing multiple bio-signs is advantageous since a combination of results may better indicate a change in a patient's condition. The presence of certain chemical markers along with changes in vital signs may allow hospital staff to more quickly diagnose the patient. Disposable IC sensors can immediately report results without having to wait for laboratory testing. The amount of blood drawn from a patient may be dramatically reduced or eliminated, which may reduce patient fatigue from blood loss. Multi-sensors also have the advantage of reduced redundancy since circuits are shared among several bio-sensors. Redundant circuits are not just a waste of money, but add to the bulk of circuits and wires that the patient has to wear.
What is desired is a re-configurable bio-sensing computing device. A bio-sensing chip that can receive inputs from several different kinds of bio-sensors and automatically configure itself is desired. A multi-input, re-configurable bio-sensing IC chip is desired. A multi-use computing platform is desirable to support a variety of types of bio-sensors. A multi-input bio-sensor computing platform is desired to read inputs from multiple sensors rather than from just a single sensor, and to share computing resources and communication bandwidth among a number of bio-sensors. A re-configurable bio-sensing computing device that can operate both from battery power when available, and by energy harvesting from RF induction or coupling is also desired.